The present invention relates to fuel injectors.
The German Patent No. DE 195 34 445 C2 describes a fuel injector. The fuel injector described in this document has an actuator disposed in an actuator space, and a valve-closure member which is operable by the actuator with the aid of a valve needle and which cooperates with a valve-seat surface to form a sealing seat. The valve needle is joined with form locking to a pressure shoulder via which the actuator acts upon the valve needle against the force of a compression spring. The pressure shoulder and the valve needle are guided in a valve housing. The actuator has a centric opening through which the valve needle projects, the actuator being braced on one side against a pressure plate and on the other side against the pressure shoulder. When the actuator expands, the valve needle is actuated contrary to the spray-discharge direction.
A disadvantage in the fuel injector known from DE 195 34 445 C2 is that the actuator has a centric opening for achieving the reversal of movement. Therefore, special actuators must be manufactured for this model type, this manufacturing also being costly. In addition, the actuator must achieve specific predefined characteristic values, particularly with respect to stability and actuating force, which is made difficult by the centric bore hole, so that the ring-shaped actuator has a considerably larger diameter compared to a solid actuator.
In summary, the known mechanical transmitting device for actuating a fuel injector, opening to the inside, with the aid of an actuator is costly.
In contrast, the fuel injector of the present invention has the advantage that any actuators can be used, particularly solid actuators without an internal bore hole. In addition, the fuel injector according to the invention can be implemented using simple components, thus permitting savings on production costs.
The supporting member is advantageously attached, preferably by welding, to a valve housing of the fuel injector. This yields a simple specific embodiment in which, in response to actuation of the actuator, the actuating sleeve moves toward the supporting member which is fixedly secured in the valve housing.
It is advantageous that the actuating sleeve has three segments arranged in relation to an axis of the actuating sleeve in a manner that they are offset by at least approximately 120xc2x0 relative to each other. This yields an actuating sleeve for which, with low structural expenditure, a uniform distribution of an actuating force of the actuator is provided over the periphery of the actuating sleeve.
It is also advantageous that the supporting member has three cut-outs arranged in relation to an axis of the fuel injector in a manner that they are offset by at least approximately 120xc2x0 relative to each other, and that at least one segment of the actuating sleeve projects through each cut-out. In this manner, a supporting member is provided which has cut-outs distributed uniformly over the periphery of the actuating sleeve, and at the same time exhibits high stability for receiving the actuating force of the actuator.
The segments of the actuating sleeve are advantageously joined at the first end of the actuating sleeve to a valve-needle plate joined to the valve needle. This yields a simple specific embodiment in which the actuator acts directly on the valve needle via the actuating sleeve.
It is advantageous that, at its second end, the actuating sleeve has a contact plate which is joined to the segments of the actuating sleeve. In this manner, an embodiment of the actuating sleeve is provided which is structurally simple to implement. In addition, the contact plate forms a flat surface against which an actuator abuts in a planar manner with a flat second end face, thereby yielding advantageous transmission of the actuating force of the actuator to the actuating sleeve.
Prestressing is advantageously applied to the actuator by a prestress spring acting on the actuator via the contact plate of the actuating sleeve. This permits a compact fuel-injector construction.
The actuating sleeve and/or the pressure plate are advantageously produced by cold-forming a metallic material. The actuating sleeve and/or the pressure plate are thereby resistant to aging and insensitive to heat; advantageous removal of the heat, developing during actuation of the actuator, from the actuator to a valve housing of the fuel injector and to the fuel is additionally provided. Furthermore, this type of production is cost-effective.